man this is an easy one don't need to think about the answer on this one..
Shoot the buggers.
I have a grey one that sighed it's death warrant when it pissed on the stainless doors of my BBQ just got to catch the prick as I am not allowed to shoot it where i live then it is going for a "swim"
over here they have caused the extinction of some native species and also have contributed to the disappearance of many ground-dwelling birds and mammals around the place...
Phil
I know that you suffer under insane gun laws. BUT, if the buggers haven't gotten around to regulating airguns yet, may I suggest a Diana Werks RWS 34 in .22 caliber? 850 feet per second in .22. It will shoot through a 1/2" plywood board at 50 yards. Plenty enough gun for possums, cats and iguanas at thirty paces or less if you can place your shots right. Quiet, and with a descent scope (either go high dollar or disposable, as a spring piston airgun will eat scopes. I have an airgun designed Weaver at about $40 and its worked fine for years). Its a sweet rifle at a low price, and findable for about $150 USD used. Its a bargain. I have used it to bag legal game, like squirells and rabbitts, and rumor has it, other critters for twenty years

. Can't say enough good about it. Buy the rifle and a can of "packed in oil" tuna, and its game over for Toonces the driving cat.

Airguns don't get enough play on this board, but a good spring piston airgun will kill a varmint just as dead as a .22 LR inside of 30-50 yards, pus they don't make much noise to keep you out of trouble with the neighbors.

FQ13